The Intramolecular Enantioselective Stetter Reaction

After this pioneering report, probably the most successful enantioselective intramolecular version of this reaction was developed by Rovis in 2002 

However, even though this reaction proceeds in a very efficient way when an aromatic aldehyde is employed as the Michael donor, the use of aliphatic aldehydes is much more problematic due to the intrinsic instability of enoliz-able aldehydes in the basic media required in the reactions catalyzed by A-heterocyclic carbenes. In fact, pre-catalyst 119a performed poorly in this case, but this limitation was overcome with the use of bicyclic triazolium salt 120a derived from phenylalanine as catalyst precursor. This new A-heterocyclic 

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